[Compression Options] Tab


The [Compression Options] tab in the SkyPDF Pro Driver print settings allows you to configure settings for the compression of images embedded in PDFs.

General

You can configure the settings to compress text and line art, to output PDF files as text, and to decrease the image’s sample point.

Text and Line Art Compression

When you check Text and Line Art Compression, text and line art (drawings) in the original document will be compressed in Zip format.
ASCII Format Check here to output the PDF file in ASCII 7 bit text format.
The PDF file output in ASCII text format can then be displayed and edited using a text editor, etc.

Downsampling

Specify interpolation and resolution for downsampling.

If you specify interpolation and resolution for downsampling, and if images with higher resolutions than that which is specified are contained in the original document, then the number of pixels will be reduced down to the specified resolution using the specified interpolation.

The resolution can be specified using number of pixels per inch (dpi). 

This setting cannot be set simultaneously with PDF/X.

BILINEAR

Interpolation method that prioritizes printing speed over print quality.

Smaller data amounts and faster processing speed.

Ideal for simple images and shapes.

BICUBIC

Interpolation method that balances printing speed and print quality.

Operation is similar to bilinear, but bicubic uses a wider area.
You can obtain images with a smoother gradation at the expense of a large amount of data.

Ideal for complex images and photos.

SUPER SAMPLING Supersampling is a method used to remove aliasing (jagged and pixelated edges, colloquially known as "jaggies") from images rendered.

Colour/Grayscale Images

You can specify the compression method for colour images and grayscale images.

JPEG2000

It is realized both improvement in image quality and compression rate, evolution of JPEG. JPEG2000 (Quality-lowest) applies maximum compression and JPEG2000 (Quality-highest) applies minimum compression. The size of the file can be reduced by compression, but the image degrades when compression is increased.

  • This setting can be set when the PDF version is 1.5 or later.
JPEG This is suitable for an image with a high resolution and large file size, or for graduated pixel images such as photographs, etc. JPEG (Quality-lowest) applies maximum compression and JPEG (Quality-highest) applies minimum compression. The size of the file can be reduced by compression, but the image degrades when compression is increased.
Run Length This is suitable for monochrome images where the black and white components have broad variation.
Zip This is suitable for comparatively small images with many components of uniform density and without graduation such as illustrations and screen shots. There is no image quality degradation in Zip compression, but the compression rate is low and the file size will be large. 
Auto select(JPEG or Zip) Can be set by selecting JPEG2000 or JPEG in [Compression Method].
If Zip format is more efficient in compressing file size than the selected compression method, Zip format is automatically applied.
The processing speed will be slow due to auto select. 

Monochrome Images

You can specify the compression method for black and white images.

A black and white image is one that is composed only of black and white. Gray is not included.

CCITT Group 3
CCITT Group 4

These are the methods that are used for fax transmission and suitable for monochrome documents created using paint software, etc. There is no loss of data by compression, and they are compatible with most compressed images.

Group 4 compresses more effectively than Group 3.

Zip This is suitable for monochrome images that have black and white components separated into fine detail.
Run Length This is suitable for monochrome images where the black and white components have broad variation.
JBIG2 This is the best compression method for reducing the file size of black and white images.